Tube/Valve Ring modulator design

[valvusmusicus]

Hi All
Have this idea for a ring modulator type circuit-inspired from the Sound Bender pullout/design that appeared in May 1974 edition of Practical Electronics in the UK
It was a phase splitter sending one output to a mixer, and the othe output went to the other mixer input, but a fet wired as a voltage controlled resistor was connected to groung-see the phots below for schematic and block diag
If you input an audio frequency into input 2, ie into the gate of the fet-the signal appearing at the input 1 will sound like a sort of ring modded signal at the output of the modulator
Its easy enough to implement a tube phase splitter and mixer. But the FET??

Someone suggested a transformer coupled triode to the line input, I guess connected in common cathode mode to ground

ANY IDEAS PLEASE??

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[piedwagtail]

This would be an empirical study in my eyes.
Less time thinking more time building.

Suggest you build everything outside C2,C3 and C5 with valve stages and get it working. Whole thing might stink. If it doesn't then research valve compressor designs, since this is near enough an audio rate compressor rather than a dynamic rate one. Some of the early Collins had bridges between transformers pulled down by triodes and I have a late period compressor idea editorial that looks very much like the fet but with a triode; being a written piece it probably functioned poorly otherwise there would have been tube commercial examples.

[slacker]

I'd just use a FET, as it's only being used a voltage controlled resistor I don't think you'll add any magic by replacing it with a valve.
You could have a look at some valve amp tremolo circuits for inspiration, that's basically what this is only running at audio speeds.

[valvusmusicus]

Thanks piedwagtail and slacker. With even my limited knowledge,thats kind of the conclusions i came to-just thought Id run it past the group. I think that actually building it and playing around with it is the best approach. Slacker, you say "I have a late period compressor idea editorial that looks very much like the fet but with a triode". Id be dead interested to see this

Many thanks all

Paul

[andrewF]

your posted circuit looks interesting enough on its own
but if you want to try tubes here are some modulator circuits to try
from Waveforms.....early 50s book

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[valvusmusicus]

THanks for that-what a great bunch of circuits to play with!
Do you have more details of the book please so I can buy it

[andrewF]

Waveforms
edited by Britton Chance... (for the) Office of Scientific Research and Development, National Defense Research Committee.
Published 1949

to be honest I have had these scans for years and never got around to trying them, so would love to hear how you go with them

[piedwagtail]

Problem is with two phases and wildly different impedances; they suggest pentode(s) for input capacitance, you might need two HV source followers on either leg to bring it into the mixer .
Lot of work, leave you to it!